A wireless fidelity (Wireless Fidelity, WiFi) technology will be popularized in and applied to the field of an intelligent transport system (Intelligent Transport System, ITS). The European Telecommunications Standards Institute (European Telecommunications Standards Institute, ETSI) claims that 802.11p of the Institute of Electrical and Electronics Engineers (Institute of Electrical and Electronics Engineers, IEEE) is used as a communications standard for an intelligent transport system.
As WiFi hotspots, that is, access points (Access Point, AP), continuously increase, WiFi network complete coverage in many cities will be realized. A WiFi transceiver module (which is equivalent to a mobile station (STA, Station)) is installed in a vehicle, such as a car, to receive real-time traffic information from a WiFi network, and WiFi network operators may charge a driver subscriber for a certain fee as a network deploying cost and network maintenance fee. A subscriber who has paid can acquire a legal certificate, and a legal STA can obtain real-time traffic information with a relatively low expense for determining a driving route in combination with navigation information.
After verifying the validity of a subscriber, a server on a WiFi network side negotiates a PTK (Pairwise Transient Key, PTK, pairwise transient key) and a group temporal key (Group Temporal Key, GTK) with the subscriber. The PTK is used for encrypting and decrypting a unicast information frame transmitted between an STA and an AP, and the GTK is used for encrypting and decrypting a broadcast information frame transmitted between an STA and an AP.
After an STA moves from an old AP to a new AP, the STA needs to acquire a GTK from the new AP for decrypting broadcast information sent by the new AP. Meanwhile, the STA leaves the old AP, and therefore, the GTK must be timely updated once an STA leaves an old AP according the stipulation of the IEEE 802.11 standard.
In the prior art, when an STA quits from a basic service set (Basic Service Set, BSS), that is, a wireless local area network, or after a GTK aging time arrives, an AP updates the GTK of the BSS, and sends the updated GTK to all STAs still in the BSS in a unicast manner.
During the implementation of the present invention, the inventor of the present invention finds that: In the prior art, in a WiFi network formed by one AP and several STAs, if an STA leaves, the AP needs to timely update a GTK, and such a GTK update mechanism applies to only a situation in which an STA position is relatively fixed. However, on a road with heavy traffic, a large number of cars installed with an STA leaves one AP for every second, and enters the coverage of another AP. One AP may be associated with a maximum of 2007 STAs. If a plurality of STAs leaves the coverage of an AP for every second, the AP needs to timely update a GTK when each STA leaves. In this case, if an AP timely updates a GTK when each STA leaves, the AP may only be busy with updating the GTK, rather than providing another service for an STA.